Method of using substituted xanthone carboxylic acid

ABSTRACT

Methods employing as the essential ingredient, novel substituted xanthone carboxylic acid compounds in the treatment of the symptons of the asthmatic condition resulting from an antigenantibody reaction. Methods for preparing these compounds and compositions and intermediates therein are also disclosed - 7 (methylthio) - xanthone - 2 - carbonylic acid is illustrated as representative of the class.

United States Patent Pfister et al.

[451 May 20, 1975 METHOD OF USING SUBSTXTUTED XANTHONE CARBOXYLIC ACID lnventors: Jurg R. Piister; Tan T. Harrison;

John H. Fried, all of Palo Alto,

Calif.

Assignee: Syntex (U.S.A.) Inc., Palo Alto,

Calif.

Filed: Dec. 18, 1973 Appl. No.: 425,885

Related U.S. Application Data Division of Ser. No. 174,259, Aug. 23, 1971, Pat. No. 3,803,174.

U.S. Cl. 424/283 Int. Cl A61k 27/00 Field of Search 424/283 References Cited UNITED STATES PATENTS 2/l972 Shen et al. 424/283 3,706,768 12/1972 Bays ..424/283 Primary Examiner-Albert T. Meyers Assistant Examiner-Norman A. Drezin Attorney, Agent, or FirmGerard A. Blaufarb; Walter H. Dreger; William B. Walker [57] ABSTRACT 14 Claims, No Drawings METHOD OF USING B TITUT N H a. base, such as sodium hydroxide, to give the corre- CARBOXYL C ACID sponding C-5 or C-7 sulfoxanthone-2-carboxylic acid;

This i a di Of ppli i n 174,259, b. ammonia, monolower alkylamine,or dilower alkylfiled A g 1, now Pat 3,303,174v 5 amine to give the corresponding G5 or C-7 sulfamoyl-,

The present invention iS directed t0 novel substituted monolower alkylsulfamoyL and dilower alkylsulfamo- Xanthone carboxylic acid compounds useful as interl mh zb li id ds, mediates for the preparation of other useful xanthone- T Compounds f the present invention are also z'cai'boxyiic acid Compounds, and t0 Compositions ful for relieving symptoms associated with allergic containing and methods utilizing these compounds as 10 m if tati h a are brought about by antigenthe essential ingredient in the treatment of symptoms antibody (allergic) reactions. In the relief of these associated with allergic manifestations, for example, t m the method employing the compounds asthmatic conditions hereof serves to inhibit the effects of the allergic reac- The present Invent on relat o 0v and tion when administered in an effective amount. While mercapto and lower alkylthio substituted xanthone-2- not intending to be bound by any theoretical mechacarboxylic acid compounds selected from those reprenism of action, the method hereof is believed to opersented by the following formulas: ate by inhibiting the release and/or the action of toxic coon 5 00" R (A) (B) and the pharmaceutically acceptable, non-toxic esters, products, eg histamine, S-hydroxytryptamine, slow amides and salts thereof; wherein R is hydrogen or releasing substance (SRS-A), and others, which are lower alkyl. produced as a result of a combination of specific anti- The compounds of the present invention, as defined body and antigen (allergic reaction). These properties by formulas (A) and (B) above, are useful as intermemake the subject compounds particularly useful in the diates for the preparation of other xanthone-Z- treatment of various allergic conditions. carboxylic acid compounds which, in turn, are useful in The present invention in a second aspect thus relates the treatment of various allergic conditions. The proto a method useful for inhibiting the effects of the allercess by which the compounds of the present invention gic reaction which comprises administering an effective are useful for preparing the other useful xanthone-2- amount of a Compound Selected from those reprecarboxylic acid compounds is described in our copend- Sented by the following formulas:

\ coon: coo

ing application 561 Ml 174,261, ROW and the pharmaceutically acceptable non-toxic esters, 3,801,598 and entitled Novel Substituted Xanthone id d salts h f; wh r in R is hydrogen or CaYbOXYliC Acid Compounds- Briefly, this Process lower alkyl; or a pharmaceutically acceptable non- Voives tmating a 07 (lower alkylthiolxamiionetoxic composition incorporating said acids, esters, am- 2-carboxylic acid or a lower alkyl ester thereof, of the id or Salts as an ti l i di t,

present invention, and prepared herein from the corresponding C-5 or C-7 mercaptoxanthone-2-carboxylic acid compounds, with:

1. a peracid, such as peracetic acid and mchloroperbenzoic, to give the corresponding G5 or G7 lower alkylsulfinylxanthone-Z-carboxylic acid compounds; or

,2. excess hydrogen peroxide to give the corresponding G5 or C-7 lower alkylsulfonylxanthone-Z- carboxylic acid compounds; or

The compounds of the present invention are also smooth muscle relaxants, e.g. bronchial dilators, and

are therefore useful in the treatment of conditions in which such agents may be indicated, as for instance in the treatment of bronchioconstriction. The compounds of the present invention are also vasodilators and are therefore useful in the treatment of conditions in which such agents may be indicated, as for instance, in renal and cardiac disorders.

treating a C5 or C-7 mercaptoxanthone-2- The present invention, in a third aspect, is directed carboxylic acid, of the present invention, with chlorine to pharmaceutical compositions useful for inhibiting under acidic conditions to give the corresponding C5 the effects of the allergic reaction comprising an effecand C chlorosulfonylxanthone-Z-carboxylic acid tive amount of a compound selected from those reprecompounds followed by treatment of the latter with Sented y he following formulas:

COOH

and the pharmaceutically acceptable esters, amides, and salts thereof; wherein R is hydrogen or lower alkyl; in admixture with a pharmaceutically acceptable nontoxic carrier.

In the practice of the method of the present invention, an effective amount of a compound of the present invention or pharmaceutical compositions thereof, as

defined above, is administered via any of the usual and like. The carriers can be selected from the various oils acceptable methods known in the art, either singly or including'those of petroleum, animal, vegetable, or synin combination with another compound or compounds thetic origin, for example, peanut oil, soybean oil, minof the present invention or other pharmaceutical eral oil, sesame oil, and the like. Water, saline,aqueous agents, such as antibiotics, hormonal agents, and so dextrose, and glycols are preferred liquid carriers, parforth. These compounds or compositions can thus be ticularly for injectable solutions. Suitable pharmaceutiadministered orally, topically, parenterally, or by inhacal excipients include starch, cellulose, talc, glucose, lation and in the form of either solid, liquid, or gaseous lactose, sucrose, gelatin, malt, rice, flour, chalk, silica dosages including tablets, suspensions, and aerosols, as l, magnesium carbonate, magnesium stereate, sodiscussed in more detail hereinafter. The administradium tearate, glyceryl monostearate, sodium chloride, tion can be conducted in single unit dosage form with d i d ki milk, l erol, ro lene glycol, water, ethcontinuous therapy or in single dose therapy ad libitum. anol, and the like. Suitable pharmaceutical carriers and in the preferred embodiments, the method of the prestheir formulation are described in Remingtons Pharent invention is practiced when relief of symptoms is eeutieal Sciences by E. W. Martin. Such composispecifically required, of p p imminent; however, tions will, in any event, contain an effective amount of the method hereof is also usefully practiced as continuth active compound together with a suitable amount ous or prophylactic treatment. of carrier so as to prepare the proper dosage form for In view of the foregoing as well as in consideration of proper administration to the host. the degree of severity of the condition being treated, Th mp nds of the present invention demonage of j and so forth, all of which factors being strate activity as inhibitors of the effects of the allergic d t mina y utin experimentation y one skilled reaction as measured by tests indicative of such activity in the art; the effective dosage in accordance herewith i l i passive cutaneous anaphylaxis as Substancan ary ver a wi rang G n rally, an ffecti tially described, for example, by J. Goose et al., Immuamount ranges from about 0.005 to about 100 mg. per l 16, 749. (1969), kg. of body weight per day and preferably from about The compounds of the present invention can be pre- 0.()l to about mg. per kg. of body weight per day. pared in accordance with the following reaction sein alternate terms, an effective amount in accordance quence;

hal

5 00 Q was e coon COOH

herewith generally ranges from about 0.5 to about 7,000 mg. per day per subject. 1

Useful pharmaceutical carriers for the preparation of the compositions hereof, can be solids, liquids, or gases. Thus, the compositions can take the form of tablets, pills, capsules, powders, sustained release formulations, solutions, suspensions, elixirs, aerosols, and the COOll I wherein each of R, R and R is lower alkyl, R and R being preferably methyl; R is hydrogen or lower alkyl; and halo is bromo, chloro, fluoro, or iodo, preferably bromo.

With reference to the above reaction sequence, an ortho or para substituted (R phenol (2) is condensed with the l,3-dicarbo(lower)alkoxyA-halobenzene compound l in the presence of cuprous oxide optionally in organic liquid reaction medium, preferably an organic amide such as dimethyl acetamide, dimethyl formamide, N-methylpyrrolidine, tetramethylurea, and so forth, to prepare the corresponding 1,3-

dicarbo(lower)alkoxy-4-(oor p-substituted phenyloxy)-benzene compound (3).

The reaction is preferably conducted in an inert organic reaction medium, such as those listed above, or. suitable mixtures of one or more of such medium. The reaction is further conducted at temperatures ranging from about 80 to about 220C, preferably from about 120 to 200C, and for a period of time sufficient to complete the reaction, ranging from about two hours to about 24 hours.

COOR

. COORS coon R 5 R with about from one to about 12 moles and the dicarbo(lower)carboxyhalobenzene compound in the presence of from about 0.5 to about 0.6 moles of the cuprous oxide. The inert organic reaction medium, if employed, is used in solvent amounts.

Thereafter, the prepared compound (3) is base hydrolyzed to give the corresponding 1,3-dicarboxy-4-(oor p-substituted phenyloxy)benzene (4). The base hydrolysis conditions'can be any employed conventionally in the art. Generally, the hydrolysis reaction is conducted using an alkali metal hydroxide at about 50 to about C. and for a period of time sufficient to complete the reaction, ranging from about 15 minutes to about 60 minutes, preferably in the presence of inert organic reaction media such as those normally employed in organic chemical reactions of this type, e.g., aqueous alkanol solutions. Although 2 moles of base are required per mole of compound (3), the amounts employed are not critical to produce the desired hydrolysis. Preferably from about three to about 5 moles of base are employed per mole of compound (3) and the reaction media, if employed, is used in solvent amounts.

The thus prepared diacid compound (4) is then cyclized with phosphoryl chloride, thionyl chloride, sulfuric acid, hydrogen fluoride, or, preferably, polyphosphoric acid (PPA), to give the corresponding 5- or 7- substituted xanthone-2-carboxylic acid compound (5). The reaction is preferably, but optionally, conducted in an inert organic reaction medium including those usually employed in organic chemical reactions, such as dimethylsulfoxide, sulfolane, benzene, toluene, and so forth. The reaction is further conducted at temperatures ranging from about 60 to about 180C, and for a period of time sufficient to complete the reaction ranging from about 15 minutes to about 90 minutes.

Although the reaction consumes the reactants on the basis of one mole of compound (4) per mole of cyclizing reagent, the reaction can be performed using any proportions of reactants. In the preferred embodiments, however, the reaction is conducted using from about 20 to about 50 moles of the cyclizing reagent per mole of starting compound (4).

The 5- and 7-1ower alkoxyxanthone-2-carboxylic acid compounds (5; R lower alkyl) thus prepared are converted to the respective 5- and 7-hydroxy compounds (5; R hydrogen) by treatment with hydrobromic or hydroiodic acid and acetic acid. This reaction is conducted at a temperature of from about 100 to about 160C. The thus prepared 5- and 7-hydroxy acid compounds are then esterified (R to give compounds (6). This reaction is conducted with ethereal diazoalkane such as diazomethane and diazoethane or with the desired lower alkyl iodide in the presence of lithium carbonate at room temperature or with the desired lower alkanol in the presence of a trace of sulfuric acid at reflux.

The hydroxy acid esters (6) are then treated with a dialkylthiocarbamoyl chloride, such as dimethylthiocarbamoyl chloride, in the presence of base, such as coon an alkali metal hydride, and in organic liquid reaction ficient to complete the reaction, ranging from about 1 hour to about 6 hours. In the preferred embodiments, the reaction is conducted by reaction of from about 1.1 to about 1.5 moles of dialkylthiocarbamoyl chloride per mole of compound (6).

The product compounds (7) are then rearranged by 65 reaction at a temperature of from about 200 to about 250C, preferably from about 220C to about 230C, and for a period of time ranging from about 1 hour to about 8 hours and in the presence of organic medium such as sulfolane, nitrobenzene, triethylene glycol and so forth, which is preferably employed in solvent amounts, to give compound (8).

Compounds (8) are then converted to the corresponding and 7-mercapto acid compounds (9) by base hydrolysis such as those described above for the preparation of compounds (4) from (3).'The 5- and 7- lower alkyl thio ether ester compounds (10) are then prepared as described above (e.g., 5 6) or by reacting compounds (9) with a lower alkyl halide in the presence of base such as potassium carbonate and organic liquid reactions medium such as those described above. The reaction is conducted at a temperature ranging from about to about 80C, preferably from to about 60C and for a period of time sufficient to complete the reaction, ranging from about 2 hours to about 16 hours.

Hydrolysis of the ester (10), as described above (e.g. 3 4), affords the 5- and 7-(loweralkylthio)-acid compounds l 1).

Alternatively, certain of the compounds of the present invention can be prepared in accordance with the following:

COOH

wherein R is lower'alkyl.

media preferably an organic amide such as those listed With reference to above Sequence B, the alkylthioabove with respect to reaction (1 2 3) to afford phenols (2) otherwise corresponding to compounds the products (7). The reaction is conducted at temper- (2) are condensed with compound' (1 as above de-.

atures ranging from about 20 to about 100C, preferascribed, to give the alkylthio compound (3'). This com-' I bly from to about C and for a period of time sufpound is then treated as depicted and described above 0 with reference to Sequence A to give the diacid compound (4) and the (alkylthio) -xanthone-2-carboxyli acid (11).

An alternative method for thepreparation of the intermediate 5- and 7-hydroxy and -lower alkoxy compounds (5) hereof is represented as follows:

Scguencc C wherein R and halo are as defined above.

With reference to Sequence C, an appropriate phenol (2) is treated with 1,3-dimethyl-4-halo-(preferably iodo) benzene (12) as described above, to prepare the corresponding 1,3-dimethyl-4-phenyloxybenzene (13). This compound is then oxidized such as with potassium permanganate in aqueous t-butanol, to give the corresponding l,3-dicarboxy-4-phenyloxybenzene (14). This compound is then cyclized, as described above, to give the corresponding xanthone-Z-carboxylic acid which can be treated as described above, to prepare the compounds of the present invention.

The acid esters of the xanthone-2-carboxylic acids hereof are prepared as described above (e.g., 5 6).

The amides of the xanthone-Z-carboxylic acids hereof are prepared by treatment of the acids with thionyl chloride followed by treatment with anhydrous ammonia or lower alkyl or dilower alkyl amine.

The salts of the xanthone-Z-carboxylic acids hereof are prepared by treating the corresponding acids with pharmaceutically acceptable base. Representative salts derived from such pharmaceutically acceptable bases include the sodium, potassium, lithium, ammonia, calcium, magnesium, ferrous, ferric, zinc, manganous, aluminum, manganic, trimethylamine, triethylamine, tripropylamine, B-(dimethylamino)ethanol, triethanolamine, fi-(diethylamino)ethanol, arginine, lysine, histidine, N-ethylpiperidine, hydrabamine, choline, betaine, ethylenediamine, glucosamine, methyl glucamine, theobromine, purines, piperazine, piperidine, polyamine resins, caffeine, procaine salts. The reaction is conducted in an aqueous solution, alone or in combination with an inert, water miscible organic solvent, at a temperature of from about 0C to about 100C, preferably at room temperature. Typical inert, water miscible organic solvents include methanol, ethanol, isopropanol, butanol, acetone, dioxane, or tetrahydrofuran. When divalent metal salts are prepared, such as the calcium salts or magnesium salts of the acids the free acid starting material is treated with about one molar equivalent of pharmaceutically acceptable base. When the aluminum salts of the acids are prepared, about one molar equivalent of the pharmaceutically acceptable base are employed.

In the preferred embodiment of the present invention, the calcium salts and magnesium salts of the acids are prepared by treating the corresponding sodium or potassium salts of the acids with at least one molar equivalent of calcium chloride or magnesium chloride, respectively, in an aqueous solution, alone or in combination with an inert water miscible organic solvent, at a temperature of from about 20C to about 100C.

In the preferred embodiment of the present invention, the aluminum salts of the acids are prepared by treating the acids with at least one molar equivalent of an aluminum alkoxide, such as aluminum triethyoxide,

aluminum tripropoxide and the like, in a hydrocarbon solvent, such as benzene, xylene, cyclohexane, and the like at a temperature of from 20C to about C.

In the present specification and claims, by the term lower alkyl is intended a lower alkyl group containing 1' to 5 carbon atoms including straight and branched chain groups and cyclic alkyl groups, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec.-butyl, t-butyl, n-pentyl, isopentyl, sec.- pentyl, t-pentyl, cyclopropyl, cyclobutyl and cyclopentyl. By the term lower alkoxy" is intended the group O-lower alkyl wherein lower alkyl" is as defined above.

By the term pharmaceutically acceptable, non-toxic esters, amides, and salts is respectively intended a lower alkyl ester, lower alkyl being as defined above; an unsubstituted, mono(lower)alkyl, or (di)- lower alkyl substituted amide, lower alkyl being as defined above; and a salt as defined above.

The nomenclature herein is employed in accordance with Chemical Abstracts 56 Subject Index (1962, January-June).

The following examples illustrate the method by which the present invention can be practiced.

EXAMPLE 1 'A mixture of 4.188 g. of 1,3-dicarbomethoxy-4- bromobenzene, 2.85 g. of p-methoxyphenol, 1.32 g. of

cuprous oxide in 20 ml. of dimethylacetamide is heated to 160C. and maintained thereat with stirring and under a nitrogen atmosphere. After monitoring via t.l.c. indicates the reaction is substantially complete, the reaction mixture is diluted with water and extracted with diethyletherzmethylene chloride (3:1). The extracts are chromatographed on 150 g. of alumina and the uniform fractions combined to give 1,3- dicarbomethoxy-4-(p-methoxyphenyloxy)-benzene. l,3-Dicarbomethoxy-4-(p-methoxyphenyloxy)- benzene (3 g.) is combined with 150 ml. of potassium hydroxide in methanol. The resultant mixture is refluxed for 1 hour after which time it is acidified, cooled, and filtered, to give l,3-dicarboxy-4-(pmethoxyphenyloxy)-benzene.

Two grams of l,3-dicarboxy-4-(p-methoxyphenyloxy)benzene in ml. of concentrated sulfuric acid is stirred at 80C. for 1 hour. After this time, the reaction mixture is poured into 200 ml. of ice water and the resultant mixture is heated on a steam bath for 15 minutes. The mixture is cooled and filtered with the precipitate being washed with water and then recrystallized from acetic acid to give 7-methoxyxanthone-2- carboxylic acid.

The foregoing procedure can be practiced using an alternative l,3-dicarboloweralkoxy-4-halo starting compound, such as l,3-dicarbomethoxy-4-chloro- (or iodo) benzene, l,3-dicarboethoxy-4-fluoro-benzene, l,3-dicarboethoxy-4-bromobenzene, and the like, with similar results. Likewise, the foregoing procedure can be practiced using an alternate 4-lower alkoxyphenol starting compound to prepare the corresponding 7- lower alkoxyxanthone-2-carboxylic acids, e.g. 7-ethoxyxanthone-Z-carboxylic acid, 7-npropoxyxanthone-Z-carboxylic acid, 7- isopropoxyxanthone-2carboxylic acid, 7-nbutoxyxanthone-Z-carboxylic acid, 7- isobutoxyxanthone-Z-carboxylic acid, 7-secbutoxyxanthone-Z-carboxylic acid, 7-tbutoxyxanthone-2-carboxylic acid, 7-npentyloxyxanthone-2-carboxylic acid, and 7- cyclopentyloxyxanthone-Z-carboxylic acid.

Likewise prepared are the corresponding C-5 substituted compounds, i.e., S-methoxyxanthone-Z- carboxylic acid, 5-ethoxyxanthone-Z-carboxylic acid, 5-n-propoxyxanthone-Z-carboxylic acid, and so forth.

The foregoing procedure can also be practiced upon the corresponding 4-(loweralkylthio)-phenol starting compounds to prepare the corresponding 05 and C-7 (lower alkylthio) substituted compounds, i.e., 7- (methylthio)-xanthone-2-carboxylic acid, 5- (methylthio)-xanthone-2-carboxylic acid, 7- (ethylthio)-xanthone-2-carboxylic acid, 5-(ethylthio)- xanthone-Z-carboxylic acid, 7-(n'propylthio)- xanthone-Z-carboxylic acid, 5-( n-propylthio xanthone-2-carboxylic acid, 7-( isopropylthio xanthone-Z-carboxylic acid, 5-( isopropylthio)- xanthone-Z-carboxylic acid, 7-(n-butylthio)-xanthonecarboxylic acid, 7-(t-butylthio)-xanthone-2-carboxylic acid, 5-(t-butylthio)-xanthone-2-carboxylic acid, 7-(npentylthio)-xanthone-2-carboxylic acid, S-(npentylthio)-xanthone-2-carboxylic acid, 7-

12 (cyclopentylthio)-xanthone-2-carboxylic acid, and 5- (cyclopentylthio)-xanthone-2-carboxylic acid.

The cyclization reaction hereof can also be performed following the procedure of Example 8.

EXAMPLE 2 The procedures of Example 1 are repeated using 0- hydroxyphenol and p-hydroxyphenol as starting compounds to respectively prepare 5-hydroXyxanthone-2- carboxylic acid and 7-hydroxyxanthone-2-carboxylic acid.

Alternatively, the hydroxy compounds can be prepared from the lower alkoxy compounds of Example 1 according to the following representative procedure.

EXAMPLE 3 A mixture of l 1 grams of 7-.methoxyxanthone-2- carboxylic acid in 100 ml. of concentrated aqueous hydrogen iodide and 100 ml. of acetic acid is refluxed for 4 hours. After this time, the mixture is cooled, diluted with water, and filtered. The precipitate is washed and dried to give 7-hydroxyxanthone-2-carboxylic acid.

EXAMPLE 4 A mixture of 4 grams of 7-hydroxyxanthone-2- carboxylic acid, 10 g. of methyl iodide, and 10 g. of lithium carbonate in 50 ml. of dimethylformamide is stirred at room temperature for a period of 16 hours. After this period of time, the reaction mixture is poured into dilute hydrochloric acid-ice and the resultant mixture extracted with ethyl acetate. The extracts are filtered through alumina to give methyl 7- hydroxyxanthone-Z-carboxylate which can be recrystallized from methanol.

EXAMPLE 5 To a solution of 6.2 g. of methyl 7-hydroxyxanthone- Z-carboxylate in 100 ml. of dimethylformamide are added 1 g. of sodium hydride. The mixture is stirred for 10 minutes at room temperature under nitrogen. Dimethylthiocarbamoyl chloride (3 g.) is then added thereto and the resultant mixture stirred at C. for 6 hours and then at room temperature for 16 hours. The mixture is then poured into 200 ml. of water containing 1 ml. of acetic acid, the resultant mixture is filtered and the solid dried to give methyl 7- dimethylthiocarbamoyloxyxanthone-Z-carboxylate.

Methyl 7-dirnethylthiocarbamoyloxyxanthone-2- carboxylate (8 g.) in 150 ml. of sulfolane is stirred at 230C. under nitrogen. After a total of 6 hours under these conditions, t.i.c. indicates the absence of starting material. The mixture is cooled to C. and ml. of hot water are slowly added. The mixture is then cooled and the filtered solid washed with water and dried to give methyl 7-(dimethylcarbamoylthio)xanthone-2- carboxylate.

Methyl 7-dimethylcarbamoylthio)-xanth0ne-2- carboxylate (7.5 g.), 10 g. of potassium hydroxide and 250 ml. of 80% aqueous ethanol is refluxed for l hour. After this time, 250 ml. of water are added and the mixture is treated with charcoal, filtered, acidified. The product is filtered off and dried to give 7- mercaptoxanthone-2-carboxylic acid.

In like manner, 5-mercaptoxanthone-2 carboxylic acid is prepared from methyl 5-hydroxyxanthone-2- carboxylate.

EXAMPLE 7 A mixture of 51.5 g. of 1,3-dimethyl-4-iodobenzene (4-iodo-m-xylene), 40 g. of p-methoxyphenol, 16 g. of cuprous oxide in 300 ml. of dimethylacetamide is heated to the boiling point and maintained under reflux 190C.) for 144 hours with stirring and under a nitrogen atmosphere. The reaction mixture is then poured into ice water and extracted with ether and the extracts are filtered through 500 g. of alumina in hexane to give 1,3-dimethyl-4-(p-methoxyphenyloxy )-benzene.

A mixture of 41 g. of 1,3-dimethyl-4-(p-methoxyphenyloxy)-benzene, 300 g. of potassium permanganate, 500 ml. of t-butanol, and 750 ml. of water is.

heated to the boiling point and maintained thereat for a period of 3 hours. After distilling off the t-butanol, the reaction mixture is filtered, the clear filtrate acidified and the precipitate of 1,3-dicarboxy-4-(pmethoxyphenyloxy)-benzene is isolated by suction filtration and washed with water.

The 1,3-dicarboxy-4-(p-methoxyphenyloxy benzene thus prepared is then cyclized as described in Example 1 or 8 hereof to give 7-methoxyxanthone-2- carboxylic acid which can be converted to 7- hydroxyxanthone-2-carboxylic acid.

In a similar manner, the foregoing procedure can be practiced utilizing other p-lower alkoxyphenol or plower alkylthiophenol starting compounds to prepare the corresponding products, for example 7- (methylthio)-xanthone2-carboxylic acid, 7-ethoxyxanthone-2-carboxylic acid, 7-(ethylthio)- xanthone-Z-carboxylic acid, 7-n-propoxyxanthone-2- carboxylic acid, 7-(n-propylthio)-xanthone-2- carboxylic acid, 7-isopropoxyxanthone-Z-carboxylic acid, 7-(isopropylthio)-xanthone-2-carboxylic acid, and so forth, which can each be converted to 7- hydroxyxanthone-Z-carboxylic acid.

EXAMPLE 8 A mixture of 1,3-dimethyl-4-bromobenzene, 10.5 g. of o-methoxyphenol, 4.65 g. of cuprous oxide, 40 ml. of tetramethylurea, and 75 ml. of N-methylpyrrolidone is stirred at 165 for 96 hours. The resultant mixture is diluted with water and extracted with methylene chloride. The methylene chloride extracts are chromatographed on 300 g. of alumina with gradient elution using hexanezether to give 1,3-dimethyl-4-(o-methoxyphenyloxy)-benzene.

A mixture of 12 g. of 1,3-dimethyl-4-(o-methoxyphenyloxy)-benzene, 72 g. of potassium permanganate, 200 ml. of t-butanol and 350 ml. of water is refluxed for 4 /2 hours. After this time, the t-butanol is distilled off, and the reaction mixture is filtered. The filtrate is aciditied to give l,3-dicarboxy-4-(o-methoxyphenyloxy)- benzene which can be recrystallized from benzenezheptane.

A mixture of 3 g. of 1,3-dicarboxy-4-(o-methoxyphenyloxy)-benzene, 75 ml. of polyphosphoric acid, and 75 ml. of sulfolane is stirred at 125C. for a period of 2 hours. After this time, the reaction mixture is poured into water, filtered and the precipitate washed. The precipitate is recrystallized from acetic acid (charcoal) to give -methoxyxanthone-2-carboxylic acid which can be converted to 5-hydroxyxanth0ne-2- carboxylic acid.

In a similar manner, the foregoing procedure can be practiced utilizing other o-lower alkoxyphenol or o- EXAMPLE 6 A mixture of 3 g. of 7-mercaptoxanthone-2- carboxylic acid in 150 ml. of dimethylformamide, 5 ml. of methyl iodide and 5 ml. of potassium carbonate is stirred for 16 hours at 60C. The mixture is then poured into dilute hydrochloric acid and the resultant mixture extracted with ethyl acetate. The extracts are chr0- matographed on alumina (methylene chloride) to give methyl 7-(methylthio)-xanthone-2-carboxylate (i.e., methyl 7-thiomethoxyxanthone-Z-carboxylate) which can be recrystallized from methylene chloride/methanol.

A mixture of 580 mg. of methyl 7- (methylthio)xanthone-Z-carboxylate, 30 ml. of ethanol, 5 ml. of saturated sodium carbonate solution and 5 ml. of water is refluxed for 1 hour. The mixture is then cooled, acidified and the precipitate filtered off to give 7-(methylthio)-xanthone-2-carboxylic acid (i.e., 7-thiomethoxyxanthone-2-carboxylic acid) as also prepared in the alternative method described in Example 1.

A mixture of 0.8 g. of 7-mercaptoxanthone-2- carboxylic acid, 2 ml. of 2-bromopropane, and excess potassium carbonate in 50 ml. of dimethylformamide is stirred for 24 hours at C. Dilute hydrochloric acid and ethanol are added, the solid filtered off and washed. The solid is saponified with sodium carbonate in aqueous methanol (30 minutes reflux). The alkaline solution is diluted with water, treated with charcoal, filtered, and acidified to give 7-(isopropylthio)-xanthone- 2-carboxylic acid which can be recrystallized from tetrahydrofuran/ethyl acetate.

In a similar manner (and alternative to the method of Example 1), the following are prepared from the respective starting compounds:

5-(methylthio)-xanthone-2-carboxylic acid,

5-(isopropylthio)-xanthone-2-carboxylic acid, 7-(ethylthio)-xanthone-2-carboxylic acid, 5-(ethylthio)-xanthone-2-carboxylic acid, 7-(n-propylthio)-xanthone-2-carboxylic acid, 5-(n-propylthio)-xanthone-2-carboxylic acid, 7-(n-butylthio)-xanthone-2-carboxylic acid, 5-(n-butylthio)-xanthone-2-carboxylic acid, 7-sec-butylthio)-xanthone-2-carboxylic acid, 5-(sec-butylthio)-xanthone-2-carboxylic acid, 7-(isobutylthio)-xanthone-2-carboxylic acid, 5-(isobutylthio)-xanthone-2-carboxylic acid, 7-(t-butylthio)-xanthone-2-carboxylic acid,

S-(t-butylthio)-xanthone-2-carboxylic acid,

7-(n-pentylthio)-xanthone-2-carboxylic acid,

5-(n-pentylthio)-xanthone-2-carboxylic acid,

7-(cyclopentylthio)-xanthone-2-carboxylic acid, and

5-(cyclopentylthio)-xanthone-2-carboxylic acid. lower alkylthiophenol starting compounds to prepare the corresponding products, for example, 5- (methylthio)-xanthone-2-carboxylic acid, 5-ethoxyxanthone-Z-carboxylic acid, 5-(ethylthio)- xanthone-2-carboxylic acid, 5-n-propoxyxanthone-2- carboxylic acid, 5-(n-propylthio)-xanthone-2 carboxylic acid, 5-isopropoxyxanthone-2-carboxylic acid, 5-(isopropylthio)-xanthone-2-carboxylic acid, and so forth, which can each be converted to 5 hydroxyxanthone-Z-carboxylic acid.

EXAMPLE 9 A mixture of 4.5 g. of 7-(methylthio)-xanthone-2- carboxylic acid, 10 g. of methyl iodide, and 10 g. of lithium carbonate in 75 ml. of dimethylformamide is stirred at room temperature for a period of 18 hours. After this period of time, the reaction mixture is poured into dilute hydrochloric acid-ice and the resultant precipitate is filtered off and washed to give methyl 7- methylthio)-xanthone-2-carboxylate.

The foregoing procedure is repeated using the alternate lower alkyl iodides so as to prepare the corre- (methylthio)-xanthone-2-carboxylate, and so forth.

In like manner, the other xanthone-Z-carboxylic acids hereof containing substituents at the G5 or C-7 positions, prepared as described above, can be converted to the corresponding acid esters, e.g. ethyl 7- mercaptoxanthone-2-carboxylate (by use of one equivalent of lithium carbonate), ethyl 5-(methylthio)- xanthone-Z-carboxylate, methyl 7-( isopropylthio xanthone-2-carboxylate, methyl 5-(isopropylthio)- xanthone-2-carboxylate, ethyl 7-( isopropylthio)- xanthone-2-carboxylate, ethyl 5-( isopropylthio xanthone-2-carboxylate, and so forth.

EXAMPLE 10 To a solution of 10 g. of 7-(methylthio)-xanthone-2- carboxylic acid in 200 ml. of ethanol is added the theoretical amount of sodium hydroxide dissolved in 200 ml. of 90% ethanol. The reaction mixture is then concentrated in vacuum to give sodium 7-(methylthio)- xanthone-2-carboxylate.

In a similar manner, the potassium and lithium salts are prepared. By replacing the sodium salt by means of an appropriate metal salt reagent, e.g. calcium chloride, manganese chloride, and so forth, the other xanthone-Z-carboxylic acid salts are prepared, e.g. magnesium 7-(methylthio)-xanthone-2-carboxylate, calcium 7-(methylthio)-Xanthone-2-carboxylate, aluminum 7-(methylthio)-xanthone-2-carboxylate, ferrous 7-(methylthio)-xanthone-2-carb0xylate, zinc 7- (methylthio)-xanthone-2-carboxylate, manganese 7- (methylthio)-xanthone-2-carboxylate, ferric 7- (methylthio)-xanthone-2-carboxylate, and so forth.

In a similar manner, the xanthone-Z-carboxylic acid salts of the other OS or G7 substituted xanthone-2- carboxylic acids hereof are prepared, e.g. potassium 5-mercaptoxanthone-2-carboxylate, sodium 7- (isopropylthio)-xanthone-2-carboxylate, sodium 5- (isopropylthio)-xanthone-2-carboxylate, and so forth.

EXAMPLE 1 1 To a mixture of 50 ml. of concentrated aqueous ammonia in 500 ml. of methanol there are added g. of 7-(ethylthio)-xanthone-2-carboxylic acid. The resultant mixture is stirred for 2 hours and is then evaporated to dryness to give the ammonium salt of 7- (ethylthio)-xanthone-2-carboxylic acid.

A solution of 10 g. of 7-ethylthioxanthone-2- carboxylic acid in 50 ml. of thionylchloride is heated at reflux for 1 hour. Thereafter, the solution is evaporated to dryness to give the corresponding acid chloride to which is added a concentrated ethereal ammonia solution. The resultant solution is evaporated giving 7- (ethylthio)-xanthone-2-carboxylic acid amide.

In like manner, the lower alkyl amides can be prepared using monoalkylamine or dialkylamine in lieu of EXAMPLE 12 To a mixture of 20 g. of procaine and 500 ml. of aqueous methanol are added 20 g. of 7-(methylthio)- xanthone-2-carboxylic acid. The resultant mixture is stirred at room temperature for 16 hours. It is then evaporated under reduced pressure, to give the procaine salt of 7-(methylthio)-xanthone-2-carboxylic acid. I

Similarly, the lysine, caffeine, and arginine salts thereof are obtained. In like manner, the e.g. procaine, lysine, caffeine, and arginine salts of the other 5- and 7-substituted xanthone-2-carboxylic acids are obtained, e. g. the procaine salt of 7-(ethylthio)-xanthone- 2-carboxylic acid, the caffeine salt of 5- (isopropylthio)-xanthone-2-carboxylic acid, the lysine salt of 7-mercaptoxanthone-2-carboxylic acid, the procaine salt of 5-(isopropylthio)-xanthone-2-carboxylic acid, and the arginine salt of 7-(t-butylthio)-xanthone- 2-carboxylic acid.

EXAMPLE 13 The following procedures illustrate the method by which the pharmaceutical compositions of the compounds hereof are prepared.

Sodium chloride (0.44 g.) is dissolved in ml. of a (9.47 g/l. water) sodium hydrogen phosphate solution. A sodium dihydrogen phosphate (8.00 g/l. water) solution (20 ml.) is then added thereto. The resultant solution having a pH of 7.38 is sterilized in an autoclave. This vehicle is then added to solid, dry 7- methylthioxanthone-Z-carboxylic acid to give a preparation suitable for intravenous injection containing 2.5 mg. of 7-methylthioxanthone-2-carboxylic acid per ml. of total composition.

EXAMPLE 14 The following procedure illustrates a test procedure for the compounds hereof.

Normal female (Sprague-Dawley) rats of 150 to 200 grams each are passively sensitized intradennally by injection of rat anti-egg albumin reaginic sera. After 24 hours, each rat is challenged intravenously with 1 ml. of 0.5% Evans blue, 1 mg. egg albumin plus 0.20 mg. of 7-methylthioxanthone-2-carboxylic acid. Control rats receive no 7-(methylthio)-xanthone-2-carboxylic acid. The dermal bluing is recorded 15 to 25 minutes later. The rats which receive the 7-(methylthio)- xanthone-Z-carboxylic acid exhibit a percent inhibition of allergic reaction whereas the control rats exhibit no inhibition.

The above procedure is repeated using 5- (methylthio)-xanthone-2-carboxylic acid, with similar results. The above procedure is repeated using oral administration, with similar results.

Inhibition of reaginic antigen-antibody reactions in rats is regarded as representative of inhibition of human reaginic allergic episodes.

Subjects challenged by antigen inhalation are measured for the extent of provoked degree of asthma condition by changes in airway resistance on expiration. The subject compounds are administered as an aerosol by inhalation before antigen challenge; Prevention of asthmatic conditions upon the administration of the compounds is evidenced by a decrease in airway resistance and other, subjective improvements, e.g. reduced cough.

What is claimed is:

l. A method for inhibiting the symptoms of the asthmatic condition resulting from an antigen-antibody reaction in a host susceptible to said reaction which comprises administering to said host an effective amount of from about 0.005 to about 100mg. per kg. of body weight per day sufficient to produce said inhibition of a compound selected from those represented by the formulas:

COOH

wherein R is hydrogen or lower alkyl; or a pharmaceutically acceptable lower alkyl ester, unsubstituted, monolower alkyl, or dilower alkyl substituted amide or salt thereof wherein said lower alkyl group contains one to five carbon atoms.

2. The method according to claim =1 wherein the compound is the compound of formula (A).

3. The method according to claim 1 wherein the compound is the compound of formula (A) in which R is hydrogen.

4. The method according to claim 1 wherein the compound is' the compound of formula (A) in which R is lower alkyl.

5. The method according to claim 1 wherein the compound is the compound of formula (A) in which R is methyl.

6. The method according to claim 1 wherein the compound is the compound of formula (B).

7. The method according to claim 1 wherein the compound is the compound of formula (B) in which R is hydrogen.

8. The method according to claim 1 wherein the compound is the compound of formula (B) in which R is lower alkyl.

9. The method according to claim 1 wherein-the compound is the compound of formula (B) in which R is methyl.

10. The method according to claim 1 wherein the compound is the acid compound of formula (A); 5- (methylthio)-xanthone-2-carboxylic acid.

11. The method according to claim 1 wherein the compound is the acid compound of formula (B); 7- (methylthio)oganthone-Z-carboxylic acid.

COOH

12. The method according to claim 1 wherein the compound is the sodium salt of the compound of formulas (A) or (B).

13. The method according to claim 1 wherein the compound is the sodium salt of the compound of formula (B).

14. The method according to claim 1 wherein the compound is the sodium salt compound of formula (B); sodium 7-(methylthio)-xanthone-2-carboxylate.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 318851038 Dated y 1975 Inventor(s) Jurg R. Pfister, Ian T. Harrison & John'H. Fried It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

v Column 14, lines 1-55 (Example 6) should follow directly after Example 5 (Column 12, lines 36-68).

Column 14, lines 56-65, are incorrectly set forth at the end of Example 6 (Column 14, lines 65, and should follow as a continuation of Example 8 (Column 13, lines 39-68) Column 13, lines l-37 (Example 7) should follow Example 6 (column 14, lines l-55) o Signed and Scaled this eighteenth D ay Of November 1 9 75 [SEAL] Arrest." Q

RUTH C. MASON C. MARSHALL DANN :I IAXII IX ll/[Fe ('umhzissimu'r nl'luu'nrs and Trademarks Q L J 

1. A METHOD FOR INHIBITING THE SYMPTOMS OF THE ASTHMATIC CONDITION RESULTING FROM AN ANTIGEN-ANTIBODY REACTION IN A HOST SUSCEPTIBLE TO SAID REACTION WHICH COMPRISES ADMINISTERINF TO SAID HOST AN EFFECTIVE AMOUNT OF FROM ABOUT 0.005 TO ABOUT 100MG. PER KG. OF BODY WEIGHT PER DAY SUFFICIENT TO PRODUCE SAID INHIBITION OF A COMPOUND SELECTED FROM THOSE REPRESENTED BY THE FORMULAS:
 2. The method according to claim 1 wherein the compound is the compound of formula (A).
 3. The method according to claim 1 wherein the compound is the compound of formula (A) in which R is hydrogen.
 4. The method according to claim 1 wherein the compound is the compound of formula (A) in which R is lower alkyl.
 5. The method according to claim 1 wherein the compound is the compound of formula (A) in which R is methyl.
 6. The method according to claim 1 wherein the compound is the compound of formula (B).
 7. The method according to claim 1 wherein the compound is the compound of formula (B) in which R is hydrogen.
 8. The method according to claim 1 wherein the compound is the compound of formula (B) in which R is lower alkyl.
 9. The method according to claim 1 wherein the compound is the compound of formula (B) in which R is methyl.
 10. The method according to claim 1 wherein the compound is the acid compound of formula (A); 5-(methylthio)-xanthone-2-carboxylic acid.
 11. The method according to claim 1 wherein the compound is the acid compound of formula (B); 7-(methylthio)-xanthone-2-carboxylic acid.
 12. The method according to claim 1 wherein the compound is the sodium salt of the compound of formulas (A) or (B).
 13. The method according to claim 1 wherein the compound is the sodium salt of the compound of formula (B).
 14. The method according to claim 1 wherein the compound is the sodium salt compound of formula (B); sodium 7-(methylthio)-xanthone-2-carboxylate. 